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H5N1 Confirmed in a Common Tern During Namibia Outbreak Affecting Around 40 Birds

Wild common tern standing beside water
Research: Disease, parasites & microbiology, Genetics & genomics

Around 40 common terns (Sterna hirundo) were found dead or showing clinical signs compatible with highly pathogenic avian influenza (HPAI) on the Namibian coast between December 2025 and January 2026. H5N1 is a subtype of influenza A virus, and highly pathogenic forms can cause severe disease and substantial mortality in susceptible birds. Only one tern in this event was laboratory-confirmed with H5N1; the wider group consisted of field cases with compatible signs or mortality. The birds were recorded on Mercury Island near Lüderitz and at Dolphin Beach near Walvis Bay.

Reported signs included depression, incoordination, respiratory distress and inability to fly. One dead common tern recovered at Dolphin Beach was submitted to Namibia’s Central Veterinary Laboratory on 30 January 2026. Testing detected influenza A virus, and the sample was then analysed with whole-genome sequencing.

The complete viral genome was characterised

Influenza A viruses have genomes divided into eight RNA segments. The researchers obtained complete or near-complete sequences for all eight, providing a genetic profile that could be compared with viruses from other regions. The virus belonged to H5N1 clade 2.3.4.4b and was classified within the EA-2024-DI.2 subgenotype — genetic lineage labels used to track closely related viruses.

One change in haemagglutinin (HA), the viral surface protein involved in binding to host cells, was relatively uncommon among available EA-2024-DI.2 sequences. The T188I substitution has been linked in previous laboratory studies to stronger binding to mammalian-type receptors, but the authors stress that increased transmissibility in living animals has not been demonstrated.

Across all eight segments, the Namibian virus grouped with EA-2024-DI.2 viruses circulating in Europe during the 2024–2025 epidemic wave. The authors say this supports a likely Eurasian origin. For six of the eight segments, it also clustered closely with a virus detected in a gull-billed tern (Gelochelidon nilotica) in Uganda in December 2024.

The exact route to Namibia remains unclear

The study does not establish the precise route by which the virus reached Namibia. The authors point to substantial gaps in genomic surveillance across Africa. Related EA-2024-DI viruses had also been reported from South Africa in 2025, but publicly available sequences were lacking, preventing a direct genetic comparison with the Namibian virus.

Namibia is an important non-breeding area for common terns from the Western Palearctic. The authors therefore highlight the species’ long-distance migration as relevant to exposure and possible movement of H5N1 between regions, while stressing that the pathway of this particular introduction cannot be reconstructed from the available data.

Previous H5N1 outbreaks have caused substantial mortality in common tern colonies elsewhere. The researchers regard the Namibian detection as a warning signal and call for stronger targeted surveillance in coastal wild birds, particularly during migration and the non-breeding season. They also emphasise expanded genomic surveillance of wild birds and poultry across Africa to improve early detection and understanding of viral dispersal.

Sources and image credit

  1. Hamunyela, E., Coetzee, L., Marcacci, M., Ancora, M., Celani, P., Secondini, B., Mincarelli, L., Monne, I., Dianati, M., & Molini, U. (2026). Highly pathogenic avian influenza H5N1 virus outbreak among common terns (Sterna hirundo) in Namibia, 2025-2026. Veterinaria Italiana, 62(2). https://doi.org/10.12834/VetIt.4031.40792.4Primary peer-reviewed short communication published 4 June 2026. Around 40 common terns were found dead or showed HPAI-compatible signs on the Namibian coast in December 2025–January 2026. A common tern submitted on 30 January 2026 yielded an H5N1 clade 2.3.4.4b virus classified as EA-2024-DI.2 after whole-genome sequencing.

Image: Rhododendrites / Wikimedia Commons — common tern at Brooklyn Bridge Park, New York City, USA, 2 August 2019. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

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